ATP and myosin binding site and myosin head

[Foggybrain]

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Which steps involved in the contraction of a skeletal muscle require binding and/or hydrolysis of ATP?

2. Dissociation of myosin head from actin filament
4. Attachment of myosin head to actin filament

Answer: 2 is correct. Why? My understanding is that when ATP is bound to myosin head = relaxed state
When ATP is hydrolysed to ADP + P, then the myosin head moves and binds to actin. Hence my answer was 4
Thanks

 

[Cornfed101]

2. Dissociation of myosin head from actin filament
4. Attachment of myosin head to actin filament

it looks like 1 and 3 are blank

 

[Foggybrain]

Yes. I understood why they were incorrect, which is why I did not include them.

 

[Cornfed101]

Yes. I understood why they were incorrect, which is why I did not include them.

I thought you said 1 was the answer?

 

[Foggybrain]

I thought you said 1 was the answer?

My apologies. The answer is 2. Question stem edited to reflect that.

 

[Cornfed101]

I like this diagram. Step 3 on here matches answer #2. There are steps in between your current understanding. The way you explained it in OP it sounded like you were skipping from 2 to 4 on my diagram

 

[Foggybrain]

Great diagram. I see where my content gap is on this topic. Thank you for showing me this pic.